louver (n.)

also louvre, early 14c., "domed turret-like structure atop a building to disperse smoke and admit light," from Old French lovier, a word of uncertain origin. One theory [OED, Barnhart] connects it to Medieval Latin *lodarium, which might be from a Germanic source (compare Old High German louba "upper room, roof;" see lobby). Skeat and Klein's sources suggest it is from French l'ouvert, literally "the open place," from le, definite article, + past participle of ouvrir "to open." Century Dictionary finds this "quite untenable."

Meaning "overlapping strips in a window" (to let in air but keep out rain) first recorded 1550s. The form has been influenced by apparently unrelated French Louvre, the name of the palace in Paris, which is said to be so named because its builder, Philip Augustus, intended it as a wolf kennel. Related: Louvered, louvred.